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<a name="C-Operators"></a>
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<a name="C-and-C_002b_002b-Operators"></a>
<h4 class="subsubsection">15.4.1.1 C and C<tt>++</tt> Operators</h4>

<a name="index-C-and-C_002b_002b-operators"></a>

<p>Operators must be defined on values of specific types.  For instance,
<code>+</code> is defined on numbers, but not on structures.  Operators are
often defined on groups of types.
</p>
<p>For the purposes of C and C<tt>++</tt>, the following definitions hold:
</p>
<ul>
<li> <em>Integral types</em> include <code>int</code> with any of its storage-class
specifiers; <code>char</code>; <code>enum</code>; and, for C<tt>++</tt>, <code>bool</code>.

</li><li> <em>Floating-point types</em> include <code>float</code>, <code>double</code>, and
<code>long double</code> (if supported by the target platform).

</li><li> <em>Pointer types</em> include all types defined as <code>(<var>type</var> *)</code>.

</li><li> <em>Scalar types</em> include all of the above.

</li></ul>

<p>The following operators are supported.  They are listed here
in order of increasing precedence:
</p>
<dl compact="compact">
<dt><code>,</code></dt>
<dd><p>The comma or sequencing operator.  Expressions in a comma-separated list
are evaluated from left to right, with the result of the entire
expression being the last expression evaluated.
</p>
</dd>
<dt><code>=</code></dt>
<dd><p>Assignment.  The value of an assignment expression is the value
assigned.  Defined on scalar types.
</p>
</dd>
<dt><code><var>op</var>=</code></dt>
<dd><p>Used in an expression of the form <code><var>a</var>&nbsp;<var>op</var>=&nbsp;<var>b</var></code><!-- /@w -->,
and translated to <code><var>a</var>&nbsp;=&nbsp;<var>a&nbsp;op&nbsp;b</var></code><!-- /@w -->.
<code><var>op</var>=</code><!-- /@w --> and <code>=</code> have the same precedence.  The operator
<var>op</var> is any one of the operators <code>|</code>, <code>^</code>, <code>&amp;</code>,
<code>&lt;&lt;</code>, <code>&gt;&gt;</code>, <code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>, <code>%</code>.
</p>
</dd>
<dt><code>?:</code></dt>
<dd><p>The ternary operator.  <code><var>a</var> ? <var>b</var> : <var>c</var></code> can be thought
of as:  if <var>a</var> then <var>b</var> else <var>c</var>.  The argument <var>a</var>
should be of an integral type.
</p>
</dd>
<dt><code>||</code></dt>
<dd><p>Logical <small>OR</small>.  Defined on integral types.
</p>
</dd>
<dt><code>&amp;&amp;</code></dt>
<dd><p>Logical <small>AND</small>.  Defined on integral types.
</p>
</dd>
<dt><code>|</code></dt>
<dd><p>Bitwise <small>OR</small>.  Defined on integral types.
</p>
</dd>
<dt><code>^</code></dt>
<dd><p>Bitwise exclusive-<small>OR</small>.  Defined on integral types.
</p>
</dd>
<dt><code>&amp;</code></dt>
<dd><p>Bitwise <small>AND</small>.  Defined on integral types.
</p>
</dd>
<dt><code>==<span class="roman">, </span>!=</code></dt>
<dd><p>Equality and inequality.  Defined on scalar types.  The value of these
expressions is 0 for false and non-zero for true.
</p>
</dd>
<dt><code>&lt;<span class="roman">, </span>&gt;<span class="roman">, </span>&lt;=<span class="roman">, </span>&gt;=</code></dt>
<dd><p>Less than, greater than, less than or equal, greater than or equal.
Defined on scalar types.  The value of these expressions is 0 for false
and non-zero for true.
</p>
</dd>
<dt><code>&lt;&lt;<span class="roman">, </span>&gt;&gt;</code></dt>
<dd><p>left shift, and right shift.  Defined on integral types.
</p>
</dd>
<dt><code>@</code></dt>
<dd><p>The <small>GDB</small> &ldquo;artificial array&rdquo; operator (see <a href="Expressions.html#Expressions">Expressions</a>).
</p>
</dd>
<dt><code>+<span class="roman">, </span>-</code></dt>
<dd><p>Addition and subtraction.  Defined on integral types, floating-point types and
pointer types.
</p>
</dd>
<dt><code>*<span class="roman">, </span>/<span class="roman">, </span>%</code></dt>
<dd><p>Multiplication, division, and modulus.  Multiplication and division are
defined on integral and floating-point types.  Modulus is defined on
integral types.
</p>
</dd>
<dt><code>++<span class="roman">, </span>--</code></dt>
<dd><p>Increment and decrement.  When appearing before a variable, the
operation is performed before the variable is used in an expression;
when appearing after it, the variable&rsquo;s value is used before the
operation takes place.
</p>
</dd>
<dt><code>*</code></dt>
<dd><p>Pointer dereferencing.  Defined on pointer types.  Same precedence as
<code>++</code>.
</p>
</dd>
<dt><code>&amp;</code></dt>
<dd><p>Address operator.  Defined on variables.  Same precedence as <code>++</code>.
</p>
<p>For debugging C<tt>++</tt>, <small>GDB</small> implements a use of &lsquo;<samp>&amp;</samp>&rsquo; beyond what is
allowed in the C<tt>++</tt> language itself: you can use &lsquo;<samp>&amp;(&amp;<var>ref</var>)</samp>&rsquo;
to examine the address
where a C<tt>++</tt> reference variable (declared with &lsquo;<samp>&amp;<var>ref</var></samp>&rsquo;) is
stored.
</p>
</dd>
<dt><code>-</code></dt>
<dd><p>Negative.  Defined on integral and floating-point types.  Same
precedence as <code>++</code>.
</p>
</dd>
<dt><code>!</code></dt>
<dd><p>Logical negation.  Defined on integral types.  Same precedence as
<code>++</code>.
</p>
</dd>
<dt><code>~</code></dt>
<dd><p>Bitwise complement operator.  Defined on integral types.  Same precedence as
<code>++</code>.
</p>

</dd>
<dt><code>.<span class="roman">, </span>-&gt;</code></dt>
<dd><p>Structure member, and pointer-to-structure member.  For convenience,
<small>GDB</small> regards the two as equivalent, choosing whether to dereference a
pointer based on the stored type information.
Defined on <code>struct</code> and <code>union</code> data.
</p>
</dd>
<dt><code>.*<span class="roman">, </span>-&gt;*</code></dt>
<dd><p>Dereferences of pointers to members.
</p>
</dd>
<dt><code>[]</code></dt>
<dd><p>Array indexing.  <code><var>a</var>[<var>i</var>]</code> is defined as
<code>*(<var>a</var>+<var>i</var>)</code>.  Same precedence as <code>-&gt;</code>.
</p>
</dd>
<dt><code>()</code></dt>
<dd><p>Function parameter list.  Same precedence as <code>-&gt;</code>.
</p>
</dd>
<dt><code>::</code></dt>
<dd><p>C<tt>++</tt> scope resolution operator.  Defined on <code>struct</code>, <code>union</code>,
and <code>class</code> types.
</p>
</dd>
<dt><code>::</code></dt>
<dd><p>Doubled colons also represent the <small>GDB</small> scope operator
(see <a href="Expressions.html#Expressions">Expressions</a>).  Same precedence as <code>::</code>,
above.
</p></dd>
</dl>

<p>If an operator is redefined in the user code, <small>GDB</small> usually
attempts to invoke the redefined version instead of using the operator&rsquo;s
predefined meaning.
</p>
<hr>
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